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Universität duisburg-essen-raabe-dd ch-kolloquium
1. Nanostructuring of 100 thousand tons
D. Ponge, J. Millan, L. Yuan, S. Sandlöbes, A. Kostka, P. Choi, T. Hickel,
J. Neugebauer, D. Raabe
Düsseldorf, Germany
WWW.MPIE.DE
d.raabe@mpie.de
30. Nov. 2011 Dierk Raabe GDCh Kolloquium Universität Duisburg-Essen
10. Effect of aging on ductility
1400
aged 450°C/48h 2 Precipitation
1200 hardening
Engineering Stress (MPa)
as-quenched
1000
increase of austenite
?
800 2 fraction during aging
1 strain 0% strain 15%
600
400
200
01
0 5 10 15 20
Engineering Strain (%)
-Fe (Martensite)
-Fe (Austenite), vol. fraction 15-20%
D. Raabe et al. Scripta Materialia 60 (2009) 1141 9
11. Effect of cold rolling after aging
20
12MnPH
18 Why so much austenite 120 K below
equilibrium transformation?
X-Ray
16
Fraction of Austenite (%)
->’ (TRIP)
14
12 formation aged
10 during (450°C/48h)
aging
8
450°C/48h
6
4
quenched
2
0
0 5 10 15 20 25 30
Cold Rolling Reduction, %
D. Raabe et al. Scripta Materialia 60 (2009) 1141 10
12. APT results: Atomic map (12MnPH aged 450°C/48h)
Martensite decorated by precipitations
Austenite ?
?
Mn atoms 70 million ions
Ni atoms Laser mode
Mn iso-concentration: 18 at.% (0.4nJ, 54K)
11
Dmitrieva et al. Acta Mater 59 (2011) 11
13. Aging-induced austenite reversion
Mn layer 1
Mn layer 2
Thermo-Calc
equilibrium Mn-conc.: M A
27 at. % Mn in austenite (A)
nominal 12 at.% Mn
3 at. % Mn in ferrite (martensite) (M) depletion zone
Mn layer 2
Mn layer 1
M A M
Mn iso-concentration (18 at.% Mn)
Dmitrieva et al. Acta Mater 59 (2011) 12
14. Aging-induced austenite reversion
Mn layer 1
Mn layer 2
Thermo-Calc
Can I push this idea further ?
equilibrium Mn-conc.: M A
A
M
27 at. % Mn in austenite (A)
nominal 12 at.%
3 at. % Mn in ferrite (martensite) (M)
aging
Excellent agreement between phase boundary
DICTRA
experiment & simulation !
Kinetic freezing and
associated austenite reversion !
Dmitrieva et al. Acta Mater 59 (2011) 13
17. Martensite relaxation & aging & nanoscale austenite reversion
at 5.45 at.% C, austenite forms at 400°C
C has ‘/’ shape in austenite layer: inheritance from austenite, Gibbs adsorption isotherm;
C on martensite grain boundaries
C has ‘V’ shape in austenite layer: austenite reversion through partitioning and kinetic freezing
16
19. Answering societies' grand challenges with complex alloys
70% of all industrial innovations are associated with progress in
materials science and engineering
Specifically, metallic materials occupy key roles
(energy, transportation, health, safety, infrastructure)
Our mission: Designing new metallic alloys from first principles
- Multiscale simulation
- Multiscale characterization starting from the atomic scale
- Synthesis, processing, testing
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